1. Field of the Invention
The present invention relates to a solid polyelectrolyte fuel cell.
2. Description of the Related Art
FIG. 10 shows a schematic diagram of a main part of a conventional solid polyelectrolyte fuel cell.
As shown in FIG. 10, on one side of a solid polyelectrolyte film 111 having proton (H+) conductivity, a fuel electrode film 112 is attached, which contains catalytic metal such as Pt—Ru and has conductivity and gas permeability. On the other side of the solid polyelectrolyte film 111, an oxide electrode film 113 is attached, which contains catalytic metal such as Pt and has conductivity and gas permeability.
On a side of the fuel electrode film 112 that is an electrode film on one side of a solid polyelectrolyte film electrode conjugate (cell) including the solid polyelectrolyte film 111, the fuel electrode film 112, the oxide electrode film 113 and the like, a first gas diffusion layer 114 having conductivity and gas diffusivity is attached so as to surround and cover the fuel electrode film 112. In other words, the first gas diffusion layer 114, which is larger than the fuel electrode film 112, is attached so as to come into direct contact with the solid polyelectrolyte film 111 as well as the fuel electrode film 112. On a side of the oxide electrode film 113 that is an electrode film on the other side of the cell, a second gas diffusion layer 115 having conductivity and gas diffusivity is attached so as to surround and cover the oxide electrode film 113. In other words, the second gas diffusion layer 115, which is larger than the oxide electrode film 113, is attached so as to come into direct contact with the solid polyelectrolyte film 111 as well as the oxide electrode film 113.
On the one side and the other side of the cell, on which the gas diffusion layers 114 and 115 are attached, respectively, separators 116 having conductivity are provided, respectively. Specifically, in the separator 116 provided on the one side of the cell, a fuel gas passage for hydrogen gas and the like is formed. Moreover, in the separator 116 provided on the other side of the cell, an oxide gas passage for air, oxygen and the like is formed.
A periphery of the solid polyelectrolyte film 111, which is exposed from peripheries of the electrode films 112 and 113 and the gas diffusion layers 114 and 115, is held by the separators 116 with sealants 117 interposed therebetween.
Note that, in FIG. 10, the gas diffusion layers 114 and 115 are closely attached to end faces of the electrode films 112 and 113 without having spaces between the end faces thereof and the layers. However, in reality, the gas diffusion layers 114 and 115 may be attached so as to come into direct contact with the solid polyelectrolyte film 111 while having spaces between the end faces of the electrode films 112 and 113 and the layers.
In the conventional solid polyelectrolyte fuel cell 110 as described above, when fuel gas is supplied to the fuel gas passage of the separator 116 and oxide gas is supplied to the oxide gas passage of the separator 116, the fuel gas is supplied to the fuel electrode film 112 while being diffused in the first gas diffusion layer 114 and the oxide gas is supplied to the oxide electrode film 113 while being diffused in the second gas diffusion layer 115. Accordingly, the fuel gas and the oxide gas electrochemically react with each other. Thus, protons (H+) generated from hydrogen gas on the fuel electrode film 112 side move toward the oxide electrode film 113 within the solid polyelectrolyte film 111. At the same time, electrons (e−) generated from the hydrogen gas on the fuel electrode film 112 side flow toward the oxide electrode film 113 through the separator 116 and the second gas diffusion layer 115 from the first gas diffusion layer 114 and the separator 116 via an external electric circuit. Thus, electricity can be generated while generating water by allowing oxygen to react with the protons and the electrons on the oxide electrode film 113 side.
<Related Arts>
A. Japanese Patent No. 3271410
B. Japanese Patent No. 3345240
C. Japanese Patent Laid-Open Publication No. 2003-123777